Parkinson's disease (PD) is a chronic and progressive degenerative disease of the brain that impairs motor control, speech, and other functions. The disease is named after English physician James Parkinson, who gave a detailed description of it in an 1817 work titled, “An Essay on the Shaking Palsy”.
Parkinson's disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, resting tremor (typically at about 5 Hz), slowing of movement (bradykinesia) and, in extreme cases, nearly complete loss of movement (akinesia). Secondary symptoms may include high level cognitive dysfunction, subtle language problems, and depression.
In contrast to many other neurological disorders, the nature of the brain degeneration that produces Parkinson's disease has been well understood for decades. The symptoms are caused by loss of nerve cells that secrete dopamine in a tiny midbrain area called the substantia nigra. These nerve cells, for reasons that are not fully understood, are especially vulnerable to damage of various sorts, including drugs, disease, and head trauma. The term Parkinsonism is used for any process that destroys large numbers of these cells and thereby causes the same characteristic symptoms. Parkinson's disease, or more fully, idiopathic Parkinson's disease, is diagnosed when no specific physical cause for the loss of dopamine cells can be identified. This is the most common situation.
The term Parkinsonism is used for symptoms of tremor, stiffness, and slowing of movement caused by loss of dopamine cells in the substantia nigra. “Parkinson's disease” is the synonym of “primary Parkinsonism”, i.e. isolated Parkinsonism due to a neurodegenerative process without any secondary systemic cause. In some cases, it would be inaccurate to say that the cause is “unknown” because a small proportion is caused by identifiable genetic mutations. It is possible for a patient to be initially diagnosed with Parkinson's disease but then to develop additional features requiring revision of the diagnosis.
There are other disorders called Parkinson-plus diseases. These include: multiple system atrophy (MSA), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and dementia with Lewy bodies (DLB). Lewy bodies are abnormal aggregates of protein that develop inside nerve cells. Most idiopathic Parkinson's disease patients also have Lewy bodies in their brain tissue, but the distribution is denser and more widespread in DLB. Even so, the relationship between Parkinson's disease, Parkinson's disease with dementia, and dementia with Lewy bodies (DLB) might be most accurately conceptualized as a spectrum, with a discrete area of overlap between each of the three disorders. The natural history and role of Lewy bodies is little understood.
These Parkinson-plus diseases may progress more quickly than typical idiopathic Parkinson disease. If cognitive dysfunction occurs before or very early in the course of the movement disorder then DLB may be suspected. Early postural instability with minimal tremor especially in the context of ophthalmoparesis should suggest PSP. Early autonomic dysfunction including erectile dysfunction and syncope may suggest MSA. The presence of extreme asymmetry with patchy cortical cognitive defects such as dysphasia and apraxias especially with “alien limb” phenomena should suggest CBD.
The usual anti-Parkinson's medications are typically either less effective or not effective at all in controlling symptoms; patients may be exquisitely sensitive to neuroleptic medications like haloperidol. Additionally, the cholinesterase inhibiting medications have shown preliminary efficacy in treating the cognitive, psychiatric, and behavioral aspects of the disease, so correct differential diagnosis is important.
Essential tremor may be mistaken for Parkinson's disease but lacks all other features besides tremor, and has particular characteristics distinguishing it from Parkinson's, such as improvement with beta blockers and alcoholic beverages (see http://en.wikipedia.org/wiki/Parkinson's_disease—cite_note-Jankovic2008-0). Wilson's disease (hereditary copper accumulation) may present with Parkinsonian features; young patients presenting with Parkinsonism or any other movement disorder are frequently screened for this rare condition, because it may respond to medical treatment. Typical tests are liver function, slit lamp examination for Kayser-Fleischer rings, and serum ceruloplasmin levels.
Parkinson's disease affects movement (motor symptoms). Other typical symptoms include disorders of mood, behavior, thinking, and sensation (non-motor symptoms). Patients' individual symptoms may be quite dissimilar and progression of the disease is also distinctly individual.
The cardinal symptoms of Parkinson's disease are:                Tremor: normally 4-6 Hz tremor, maximal when the limb is at rest, and decreased with voluntary movement. It is typically unilateral at onset. This is the most apparent and well-known symptom though an estimated 30% of patients have little perceptible tremor; these are classified as akinetic-rigid.        Rigidity: stiffness; increased muscle tone. In combination with a resting tremor, this produces a ratchety, “cogwheel” rigidity when the limb is passively moved.        Akinesia/bradykinesia: absence of movement and slowness, respectively. Rapid, repetitive movements produce a dysrhythmic and decremental loss of amplitude.        Postural instability: failure of postural reflexes, which leads to impaired balance and falls.        
Other motor symptoms include gait and posture disturbances:                Shuffling: gait is characterized by short steps with feet barely leaving the ground, producing an audible shuffling noise. Small obstacles tend to cause the patient to trip.        Decreased arm-swing.        Turning “en bloc”: rather than the usual twisting of the neck and trunk and pivoting on the toes, Parkinson's disease patients keep their neck and trunk rigid, requiring multiple small steps to accomplish a turn.        Stooped, forward-flexed posture: In severe forms, the head and upper shoulders may be bent at a right angle relative to the trunk (camptocormia).        Festination: a combination of stooped posture, imbalance, and short steps. It leads to a gait that gets progressively faster and faster, often ending in a fall.        Gait freezing: “freezing” is a manifestation of akinesia (an inability to move). Gait freezing is characterized by an inability to move the feet which may worsen in tight, cluttered spaces or when attempting to initiate gait.        Dystonia (in about 20% of cases): abnormal, sustained, painful twisting muscle contractions, often affecting the foot and ankle (mainly toe flexion and foot inversion), which often interferes with gait.        
Speech and swallowing disturbances:                Hypophonia: soft speech. Speech quality tends to be soft, hoarse, and monotonous. Some people with Parkinson's disease claim that their tongue is “heavy” or have cluttered speech.        Monotonic speech.        Festinating speech: excessively rapid, soft, poorly-intelligible speech.        Drooling: most likely caused by a weak, infrequent swallow and stooped posture.        Dysphagia: impaired ability to swallow; may lead to aspiration pneumonia.        
Other motor symptoms:                Fatigue (up to 50% of cases).        Masked faces (a mask-like face also known as hypomimia), with infrequent blinking.        Difficulty rolling in bed or rising from a seated position.        Micrographia (small, cramped handwriting).        Impaired fine motor dexterity and motor coordination.        Impaired gross motor coordination.        Akathisia: the inability to sit still.        
Parkinson's disease causes cognitive and mood disturbances, being in many cases related. Estimated prevalence rates of depression vary widely according to the population sampled and methodology used. Reviews of depression estimate its occurrence in anywhere from 20-80% of cases. Estimates from community samples tend to find lower rates than from specialist centres. Most studies use self-report questionnaires such as the Beck Depression Inventory, which may overinflate scores due to physical symptoms. Studies using diagnostic interviews by trained psychiatrists also report lower rates of depression. More generally, there is an increased risk for any individual with depression to develop Parkinson's disease at a later date. Seventy percent of individuals with Parkinson's disease diagnosed with pre-existing depression go on to develop anxiety. Ninety percent of Parkinson's disease patients with pre-existing anxiety subsequently develop depression, apathy or abulia.
Cognitive disturbances include:                Slowed reaction time: both voluntary and involuntary motor responses are significantly slowed.        Executive dysfunction, characterized by difficulties in: differential allocation of attention, impulse control, set shifting, prioritizing, evaluating the salience of ambient data, interpreting social cues, and subjective time awareness. This complex is present to some degree in most Parkinson's patients; it may progress to:                    Dementia: a later development in approximately 20-40% of all patients, typically starting with slowing of thought and progressing to difficulties with abstract thought, memory, and behavioral regulation. Hallucinations, delusions and paranoia may develop.            Short term memory loss: procedural memory is more impaired than declarative memory. Prompting elicits improved recall.            Non-motor causes of speech/language disturbance in both expressive and receptive language: these include decreased verbal fluency and cognitive disturbance especially related to comprehension of emotional content of speech and of facial expression.            Difficulty deceiving others that links to prefrontal hypometabolism.            Medication effects: some of the above cognitive disturbances are improved by dopaminergic medications, while others are actually worsened.                        
Movement disorders are neurological conditions that affect the speed, fluency, quality, and ease of movement. Abnormal fluency or speed of movement (dyskinesia) may involve excessive or involuntary movement (hyperkinesia) or slowed or absent voluntary movement (hypokinesia).
Movement disorders include the following conditions:                Ataxia (lack of coordination, often producing jerky movements)        Dystonia (causes involuntary movement and prolonged muscle contraction)        Huntington's disease (also called chronic progressive chorea)        Multiple system atrophies (e.g., Shy-Drager syndrome)        Myoclonus (rapid, brief, irregular movement)        Parkinson's disease        Progressive supranuclear palsy (rare disorder that affects purposeful movement)        Restless leg syndrome (RSD) and periodic limb movement disorders (PLMD)        Tics (involuntary muscle contractions)        Tourette's syndrome        Tremor (e.g., essential tremor, resting tremor)        Wilson disease (inherited disorder that causes neurological and psychiatric symptoms and liver disease).        
Common dystonias include spasmodic torticollis, which affects muscles of the head, face, and neck; and blepharospasm, which causes involuntary closing of the eyelids.
Tourette's syndrome is an inherited disorder characterized by multiple motor and vocal tics (repeated muscle contractions). Symptoms of Tourette's syndrome usually develop during childhood or early adolescence. Patients with the disorder often develop behavioral problems such as hyperactivity, inattention, impulsivity, obsessions, and compulsions. In most cases, symptoms vary in frequency and in severity.
Tics are involuntary muscle contractions that interrupt normal activities. They often are preceded by a strong sensation or urge that is temporarily relieved following the muscle contraction. Examples of common tics include the following: blinking, clearing the throat, facial twitching, grunting, shrugging the shoulders, and sighing.
Movement disorders occur as a result of damage or disease in a region located at the base of the brain (basal ganglia). The basal ganglia are comprised of clusters of nerve cells (neurons) that send and receive electrical signals and are responsible for involuntary movement. Movement disorders may result from at least one of the following: age-related changes, environmental toxins, genetic disorders (e.g., Huntington's disease, Wilson disease), medications (e.g., antipsychotic drugs), metabolic disorders (e.g., hyperthyroidism), Parkinson's disease, and stroke.
Neurologic Diseases are disorders of the brain, spinal cord and nerves throughout the body. Together they control all the workings of the body. When something goes wrong with a part of the nervous system, an individual may have trouble moving, speaking, swallowing, breathing or learning. The individual may also have problems with memory, senses or mood.
Currently there are more than 600 neurologic diseases. Thus, neurological disorders are disorders that can affect the central nervous system (brain and spinal cord), the peripheral nervous system, or the autonomic nervous system. Major conditions include:                behavioral/cognitive syndromes        headache disorders such as migraine, cluster headache and tension headache        epilepsy        traumatic brain injury        neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (Lou Gehrig's disease)        cerebrovascular disease, such as transient ischemic attack and stroke        sleep disorders        cerebral palsy        infections of the brain (encephalitis), brain meninges (meningitis), spinal cord (myelitis)        infections of the peripheral nervous system        neoplasms: tumors of the brain and its meninges (brain tumors); spinal cord tumors, tumors of the peripheral nerves (neuroma)        movement disorders, such as Parkinson's disease, Huntington's disease, hemiballismus, tic disorder, and Tourette's syndrome        demyelinating diseases of the central nervous system, such as multiple sclerosis, and of the peripheral nervous system, such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP)        spinal cord disorders: tumors, infections, trauma, malformations (e.g., myelocele, meningomyelocele, tethered cord)        disorders of peripheral nerves, muscle (myopathy) and neuromuscular junctions        exciting injuries to the brain, spinal cord and peripheral nerves        altered mental higher status, encephalopathy, stupor and coma        speech and language disorders; functional symptoms, having no apparent physiological cause; and        paraneoplastic neurological syndromes.        
Chronic Pain Overview: While acute pain is a normal sensation triggered in the nervous system to alert an individual to possible injury and the need to take care of the situation or issue, chronic pain is different. Chronic pain persists. Pain signals keep firing in the nervous system for weeks, months, even years. There may have been an initial mishap, e.g.: sprained back, serious infection, or there may be an ongoing cause of pain, e.g.: arthritis, cancer, ear infection, but some people suffer chronic pain in the absence of any past injury or evidence of body damage.
Many chronic pain conditions affect older adults. Common chronic pain complaints include headache, low back pain, cancer pain, arthritis pain, neurogenic pain (pain resulting from damage to the peripheral nerves or to the central nervous system itself), psychogenic pain (pain not due to past disease or injury or any visible sign of damage inside or outside the nervous system).
Medications, acupuncture, local electrical stimulation, and brain stimulation, as well as surgery, are some treatments for chronic pain. Some physicians use placebos, which in some cases has resulted in a lessening or elimination of pain. Psychotherapy, relaxation and medication therapies, biofeedback, and behavior modification may also be employed to treat chronic pain. Many people with chronic pain may be helped if they understand the causes of pain and the many and varied steps that can be taken to undo what chronic pain has instantiated.